1. Field of the Invention
The present invention relates to a printed wiring board formed with a core substrate, an upper buildup layer and a lower buildup layer.
2. Description of Background Art
Japanese Laid-Open Patent Publication No. 2011-100908 relates to a printed wiring board having through holes (penetrating holes) formed by using a laser. In Japanese Laid-Open Patent Publication No. 2011-100908, a printed wiring board has a through hole that becomes narrower from an upper surface toward a lower surface of a core substrate and a through hole that become narrower from the lower surface toward the upper surface so that warping of the printed wiring board is reduced. The entire contents of this publication are incorporated herein by reference.